Measurement of J and dipolar couplings from simplified two-dimensional NMR spectra.

Simple procedures are described for recording complementary in-phase and antiphase J-coupled NMR spectra. The sum and difference of these spectra contain only the upfield and the downfield components of a doublet, making it possible to measure the J splitting directly from these combinations without an increase in resonance overlap relative to the decoupled spectrum. The approach is demonstrated for measurement of 1JNH splittings and 2JHNC splittings in oriented and isotropic ubiquitin. Dipolar couplings obtained from differences in the splittings measured in the oriented and isotropic phases are in excellent agreement with dipolar couplings obtained from direct measurement of the splitting or from a conventional E. COSY-type measurement.